1. Field of the Disclosure
The disclosure relates to a liquid crystal display device, and more particularly, to an array substrate for a reflective type or transflective type liquid crystal display device improving reflection efficiency and a method of fabricating the same.
2. Discussion of the Related Art
With rapid development of information technologies, electronic display devices for displaying the information have been actively proposed and developed. More particularly, flat panel display (FPD) devices having a thin profile, light weight and low power consumption have been actively pursued. FPD devices can be classified into an emissive type and a non-emissive type depending on their light emission capability. In an emissive type FPD device, an image is displayed using light that emanates from the FPD device. In a non-emissive type FPD device, an image is displayed using light from an external source that reflects and/or transmits through the FPD. For example, a plasma display panel (PDP) device and a field emission display (FED) device are an emissive type. In another example, an electroluminescent display (ELD) device is an emissive type FPD device. Unlike a PDP and an ELD, a liquid crystal display (LCD) device is a non-emissive type FPD device that uses a backlight as a light source.
Among the various types of FPD devices, liquid crystal display (LCD) devices have been widely used as monitors for notebook computers and desktop computers because of their high resolution, good color rendering capability and superiority in displaying moving images. The LCD device displays images by controlling a transmittance of light through the device. More particularly, liquid crystal molecules interposed between two substrates facing each other modulate light transmission in response to an electric field generated between electrodes on the substrates.
Because the LCD device does not emit light, the LCD device needs a separate light source. Thus, a backlight is disposed on the rear surface on a liquid crystal panel of the LCD device, and images are displayed with the light emitted from the backlight and transmitted through the liquid crystal panel. Accordingly, the above-mentioned LCD device is referred to as a transmissive type LCD device. The transmissive type LCD device can display bright images in a dark environment due to the use of a separate light source, such as a backlight, but may result in large power consumption because of the use of the backlight.
To solve the problem of the large power consumption, a reflective type LCD device has been developed. The reflective type LCD device controls transmittance of light by reflecting the outside natural light or artificial light through a liquid crystal layer. In a reflective type LCD device, a pixel electrode on a lower substrate is formed of a conductive material having a relatively high reflectance and a common electrode on an upper substrate is formed of a transparent conductive material.
FIG. 1 is a cross-sectional view of illustrating an array substrate for a reflective type LCD device according to the related art. FIG. 1 shows a pixel region including a thin film transistor.
In FIG. 1, a thin film transistor Tr including a gate electrode 15, a gate insulating layer 20, a semiconductor layer 25, and source and drain electrodes 33 and 36 is formed on a substrate 10, on which a gate line (not shown) and a data line 30 cross each other to define a pixel region P.
A first passivation layer 39 of an inorganic insulating material is formed on the thin film transistor Tr. A second passivation layer 45 of an organic insulating material is formed on the first passivation layer 39. The second passivation layer 45 has an embossed surface. A third passivation layer 49 of an inorganic insulating material is formed on the second passivation layer 45. The first, second and third passivation layers 39, 45 and 49 have a drain contact hole 47 exposing the drain electrode 36.
A reflector 52 is formed on the third passivation layer 49 in the pixel region P. The reflector 52 is formed of a metallic material having relatively high reflectance. The reflector 52 contacts the drain electrode 36 through the drain contact hole 47 and functions as a reflective electrode. The reflector 52 and the third passivation layer 49 have embossed surfaces due to the embossed surface of the second passivation layer 45.
The reflective type LCD device including the reflector 52 of the embossed surface has higher reflection efficiency and visibility than a reflective type LCD including a flat surface of a reflector.
However, the reflectance in the reflective type LCD device including the reflector 52 of the embossed surface is about 65%. A reflective type LCD device having more improved reflection efficiency and visibility has been needed for personal mobile devices.